Plastic cover having metal reinforcement for internal combustion engine applications and method of construction

ABSTRACT

A cover assembly for an internal combustion engine application and method of construction therefore provides one construction for a valve cover assembly, and another construction for an end cover assembly for a crankcase. The cover assemblies include at least one rigid metal carrier having a plurality of bolt openings and a plurality of load limiters located about said openings. A material is overmolded on the carrier and about the load limiters, with the material forming an exposed sealing surface for direct engagement with a seal gasket.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 11/673,316, filed Feb. 9, 2007, which claims the benefit of U.S.Provisional Application Ser. No. 60/772,293, filed Feb. 10, 2006, andU.S. Provisional Application Ser. No. 60/772,294, filed Feb. 10, 2006,all of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to internal combustion engines, andmore particularly plastic covers for internal combustion engineapplications.

2. Related Art

Covers for internal combustion engine applications, such as valve coversand rear engine covers for automotive and other internal combustionengine applications typically are made of die cast metal, metalstampings or molded thick-walled thermoset or thermoplastics materials.The covers typically have an elongated trough-like structure and have aperimeter flange formed with a series of spaced bolt holes that enablethe cover to be bolted onto an associated cylinder head or rear portionof the engine. Use of the above materials (including the thick-walledplastics materials) is due in large part to the requirement that thecover have sufficient structural stiffness and stability under changingoperational conditions (e.g., temperature, vibration, loading) tosupport and maintain a good seal with a seal gasket that is typicallyplaced between the valve cover and the cylinder head to avoid oilleakage between the cover and head.

The all-metal valve covers are common, but are costly and heavy. Thethick-walled all-plastic valve covers can be less costly and cancontribute to a reduction in weight, but often the structural anddimensional stability requirements call for such large wall thicknessesthat the benefits offered by the plastics material are offset by thebulkiness of the product and space requirements taken up by the addedwall thickness. The thermoset materials are relatively stiffer than thethermoplastics materials, but they are more costly. Another issue withall-plastic covers is the need for added fasteners as compared to theall-metal covers in order to adequately prevent leakage. As such, thespan between adjacent bolt holes is decreased and the number offasteners is increased compared to metal valve covers, thus, adding tothe cost and weight of the valve cover assembly. To date, a commerciallysuitable plastic valve cover that takes advantage of the benefits ofwhat plastics have to offer has not been fully exploited, due in largepart to the structural and dimensional limitations of the availableplastics materials.

SUMMARY OF THE INVENTION

The present invention overcomes or greatly minimizes the foregoinglimitations of the known prior art valve cover assemblies.

A cover assembly for a valve cover or rear engine cover according to apresently preferred embodiment of the invention comprises a rigid metalcarrier or frame structure that is overmolded with plastics material.

According to one feature of a valve cover constructed in accordance withthe invention, a metal carrier of the valve cover includes a pluralityof arch-shaped truss portions that are spaced laterally from one anotheralong the length of the valve cover assembly, at least some of which arespaced from opposite longitudinal ends of the assembly.

According to another feature of a cover constructed in accordance withthe invention, a metal carrier of the cover assembly includes flangereinforcement portions that extend along a perimeter of the coverassembly. The flange reinforcement portions are formed with a pluralityof bolt hole openings that are spaced from one another.

According to still another feature of a cover constructed in accordancewith the invention, a plastics material is overmolded about an undersidemounting surface of the flange reinforcement portions to provide asealing surface of the assembly for direct engagement with a sealgasket.

According to yet a further feature of a cover constructed in accordancewith the invention, the plastics material is preferably a thermoplasticsmaterial and is of a relatively thin-walled construction. Bythin-walled, it is meant that the wall thickness of the plasticsmaterial would be insufficient in itself (i.e., without the metalcarrier) to be suitable for a valve cover for the intended application.

According to yet another feature of a cover constructed in accordancewith the invention, the metal carrier is fabricated of stamped metalmaterial

Covers constructed in accordance with the invention have the advantageof having thin-walls with structural and dimensional integrity normallyassociated with all-metal covers.

Covers constructed in accordance with the invention also have thefurther advantage of having fewer bolt holes (and thus requiredfasteners) than an equivalent all-plastic cover.

Additionally, covers constructed in accordance with the invention havethe further advantage of providing attaining all of the cost and weightsaving advantages of plastic due to the plastic overmold, in combinationwith the structural and dimensional advantages of metal, due to themetal carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will becomemore readily appreciated when considered in connection with thefollowing detailed description of the presently preferred embodiments,appended claims and drawings, wherein:

FIG. 1 is a perspective view of a valve cover assembly constructedaccording to a presently preferred embodiment of the invention;

FIG. 2 is a perspective view of an arch portion of a metal carrier frameof the valve cover assembly;

FIG. 3 is a perspective view of the metal carrier frame;

FIG. 4 is a plan view of the assembly of FIG. 1;

FIG. 5 is a cross-sectional view taken generally along line 5-5 of FIG.4;

FIG. 6 is a rear perspective view of a rear engine cover assemblyconstructed according to another presently preferred embodiment of theinvention;

FIG. 7 is a front perspective view of the rear engine cover assembly;

FIG. 8 is partially exploded perspective view of a metal carrier frameof the rear engine cover assembly;

FIG. 9 is a plan view of the assembly of FIG. 7; and

FIG. 10 is a cross-sectional view taken generally along line 10-10 ofFIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A cover assembly for an internal combustion engine (not shown),represented here as a valve cover assembly constructed according to apresently preferred embodiment of the invention, is shown generally at10 in FIGS. 1 and 4. The valve cover assembly 10 has a body 12 that maybe dome-shaped and elongated to provide a generally trough-shapedstructure. The body 12 extends longitudinally between opposite ends 14,16 and laterally between opposite sides 18, 20. The assembly 10 includesa mounting flange 22 that encircles an outer perimeter 23 of the body12. Side portions 24, 26 of the flange 22 extend along the sides 18, 20of the body 12 and are formed with a plurality of bolt holes 28 foraccommodating a corresponding plurality of fasteners (not shown) used tomount the cover 10 to a cylinder head (not shown) of the internalcombustion engine.

As shown in FIG. 3, the valve cover assembly 10 includes a metalreinforcement carrier or frame shown generally at 30, which may be madeof stamped steel, for example. The reinforcement or carrier 30 isovermolded with a plastics material 32 that closes the spaces betweenmembers of the carrier 30 and completes the general shape of theassembly 10. The carrier 30, being over molded, is at least partiallyembedded, and shown here as being completely embedded or encapsulated inthe plastics material 32. The carrier 30 serves to provide rigidstructural support and dimensional integrity to the plastics material32.

As shown in FIGS. 2 and 3, the carrier 30 includes a plurality ofarch-shaped trusses or beams 34 that extend laterally across the valvecover assembly 10 crosswise and generally perpendicular to thelongitudinal direction generally between the opposite sides 18, 20. Asillustrated, the trusses 34 take the general cross-sectional shape ofthe body 12 of the assembly 10 and are spaced laterally from another. Atleast some of the trusses 34 are spaced from the ends 14, 16 of theassembly 10, and thus, reside generally in the mid region of the body12. As such, the trusses 34 enable use of a relatively thin-walled layerof the plastics material 32 in comparison to a cover not having trusses,wherein the trusses 34 act to reduce deflection of the cover assembly 10and add structural integrity to the assembly 10 across its width andover its length.

The carrier 30 may further include flange support portions 36.Preferably, a pair of laterally spaced flange support portions 36 serveto reinforce the mounting flange 22, and in particular the laterallyspaced side portions 24, 26 of the flange 22. The overmolded plasticsmaterial 32 surrounds or encapsulates the portions 36, including anunderside mounting surface 38 directly beneath the portions 36.Accordingly, an exposed surface 39 (FIG. 5) of the overmolded plasticsmaterial 32 overlying the frame 30 serves as the sealing surface forengaging a seal gasket (not shown) of the internal combustion enginethat is positioned between the cover assembly 10 and the cylinder head(not shown).

The flange support portions 36 include a plurality of bolt holes 40 thatcorrespond to the bolt holes 28 of the assembly 10. As such, the metalcarrier 30 surrounds each bolt hole 28 and extends between adjacent boltholes 28, providing structural and dimensional support and integrity tothe flange 22.

The trusses 34 and flange support portions 36 may be separate orconnected to one another as a sub-assembly. As such, the trusses 34 maybe fixed to the side flange supports 36, such as via a weld joint, forexample, or, as shown in FIGS. 3 and 5, they may be separate anddetached from one another.

The plastics material of the overmold 32 may be fabricated of a suitablethermoplastics material. The overmold 32 may also be fabricated of athermoset material. The overmold 32 may be formed of other material aswell, including but not limited to rubber, magnesium and aluminum, forexample.

The metal carrier 30 provides the main support for the assembly 10,while the overmolded plastics material 32 connects the flange supports36 and trusses 34 of the carrier 30 together and serves to reinforce thecarrier 30 (and also to form the enclosure function of the cover 10). Tofurther enhance the structural rigidity of the carrier 30, and thus, thecover assembly, the trusses 34 and flange support portions 36 of thecarrier 30 may include reinforcement ridges, ribs or embossments 42 thatextend outwardly from a generally flat plane (P, FIG. 5) traversed bythe trusses 34 and flange support portions 36. The embossments 42 canfurther act as load limiters about the bolt holes 28 to reduce thepossibility of deflection or over compression of the mounting flange 22.

The cover assembly 10 allows die cast covers or relatively thick-walledplastics covers to be replaced with less expensive and thinner-walledmetal/plastic composite construction of the present invention. Theassembly 10 uses less plastics material than the all-plastics covers andweighs less, while maintaining equivalent or better structuralperformance than the all-metal covers. Because of the increasedstructural stiffness provided by the carrier 30, larger bolt spansbetween adjacent bolt holes 28 are possible, and thus, the cover 10 canbe mounted with fewer fasteners than that required for traditionalall-plastic covers. By way of example and without limitation, in a valvecover normally requiring twelve fasteners in an all-plastic thermosetcover, only ten or fewer fasteners would now be required using thepresent assembly 10. The assembly 10 also has improved dimensionalstability and resistance to creep as compared to an all plastic cover ofequivalent application.

In FIGS. 6 and 7, another aspect of a cover assembly in accordance withthe invention, shown as a rear engine cover assembly constructedaccording to a presently preferred embodiment, is shown generally at 50.Plastic covers traditionally use a press-in-place style gasket tocompensate for the increased amount of deflection and the creep of theplastic over time as compared to a metallic cover. Traditional metalrear covers (such as die cast aluminum) are able to use a flat “LEM”(liquid Eastover molding) gasket, which is less expensive than thepress-in-place gasket variety, because of the reduced deflection of thealuminum die casting. Accordingly, if an all plastic cover is providedas a lower cost solution compared to the aluminum die cast cover, thehigher priced press-in-place gasket would be needed, and thus, mayoffset any potential cost savings by using plastic.

The carrier/plastic rear cover assembly 50 construction described hereinand shown in FIGS. 6 and 7 allows the lower cost gasket solution (LEM)to be utilized due to the reduced deflection of the cover assembly 50 ascompared to an all plastic cover. As such, the overall cost of theassembly 50 in use is reduced in comparison to all plastic covers. As inthe valve cover assembly 10 above, by using a stamped metal carrier 52(FIG. 8) around an outer perimeter 54 and around a crankshaft seal bore56, the deflection of the overmolded plastic/metal cover assembly 50 canbe reduced. Further, the metal carrier 52 allows a thin wall of standardlow cost thermoplastic material to be molded over the metal carrier 52to form a body 58 of the cover assembly 50. Another benefit of thestamped steel carrier 52 is the ability to form or incorporate boltlimiters 60 in place. By using the lower cost thermoplastic body 58 withthe over molded steel carrier 52, a less expensive cover assemblyresults in comparison to those utilizing separate load limiters incombination with thick walled plastics, or all metal covers.

The carrier 52 includes a perimeter portion 62 shaped to extend aroundthe outer perimeter 54 of the assembly, and preferably continuouslythereabout, and a bore portion 64 shaped to extend around the crankshaftseal bore opening 56, and preferably continuously thereabout. Bothportions 62, 64 have ridges, ribs or embossments 66 to stiffen therespective portions 62, 64. The perimeter portion 62 has spaced holes 68for receipt of the fasteners (not shown), wherein the holes 68 aresurrounded by the embossments 66 to assist in reducing deflection, whilealso acting as bolt limiters. In addition to the embossments 66,additional load limiting features 60 can be incorporated to furtherreduce deflection of the assembly 50 upon tightening the fasteners.These load limiting features 60 are preferably exposed even afterovermolding. The load limiting features 60 can be made of the same or ofa different material than that of the perimeter portion 62. For example,the perimeter portion 62 can be made of steel, while the load limitingfeatures 60 could be made of stainless steel, by way of example andwithout limitation. Accordingly, the perimeter portion 62 serves as acarrier for the load limiting features 60. It should be recognized thatthe load limiting features 60 could be molded in place via theovermolded body 58, or they could also be attached to the perimeterportion 62, such as by way of a weld joint, for example.

As such, the cover assembly 50, although constructed in large part fromthe lightweight plastics material body 58, can provide a secure andreliable attachment and remain reliably sealed to the crankcase in use.This is due to the incorporation of the metal carrier 52 into the body58, and further made possible by the addition of the load limitingfeatures 60.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

1. A cover assembly for an internal combustion engine application,comprising: at least one rigid metal carrier having a plurality of boltopenings; a plurality of load limiters, said load limiters being locatedadjacent said openings; a material overmolded on said carrier and aboutsaid load limiters, said material forming an exposed sealing surface fordirect engagement with a seal gasket; and wherein said cover is a rearcrankcase cover further comprising a metal annular carrier overmolded bysaid material, said annular carrier encircling a crank shaft seal bore.2. The cover of claim 1 wherein said load limiters are formed about saidbolt openings as one piece with said rigid metal carrier.
 3. The coverof claim 1 wherein said load limiters are formed separately from saidrigid metal carrier.
 4. The cover of claim 3 wherein said rigid metalcarrier and said load limiter are constructed from materials having adifferent material content.
 5. The cover of claim 1 wherein said atleast one rigid metal carrier and said annular carrier are stampedsteel.
 6. The cover of claim 1 wherein said material is a thermoplastic.7. A method of constructing a rear engine cover assembly for an internalcombustion engine application, comprising: stamping a rigid metalcarrier having a perimeter portion shaped to extend around an outerperimeter of the assembly and a bore portion shaped to extend around abore of a crankshaft; forming a plurality of bolt openings in saidperimeter portion; and overmolding said perimeter portion and said boreportion with a plastic material to form a body of said rear engine coverassembly and forming a sealing surface with said plastic materialbeneath said perimeter portion.
 8. The method of claim 7 furtherincluding forming separate load limiters in the material of saidperimeter portion about said bolt openings.
 9. The method of claim 7further including stamping said carrier from steel.
 10. The method ofclaim 7 further including providing said plastic material as athermoplastic.
 11. The method of claim 7 further including disposingbolt limiters in said bolt openings and fixing said bolt limiterstherein by at least partially overmolding said bolt limiters with saidplastic material.